1. Technical Field
The present invention relates to light source devices and projectors and, in particular, to a technique for a light source device using a laser light.
2. Related Art
A projector displaying an image by using a light emitted from a light source device has become widespread. For example, there is a projector having transmissive liquid crystal display panels for a red (R) light, a green (G) light, and a blue (B) light and a light combining optical apparatus which combines the lights modulated by the transmissive liquid crystal display panels. In such a projector, if the polarization direction of the light emitted from the light source device is random, light loss in the transmissive liquid crystal display panels becomes large. Therefore, it is necessary to align the polarization directions in a predetermined direction by using a polarization conversion element.
The polarization conversion element includes a polarization separation element and a polarization rotation element, for example. The polarization conversion element separates the incident light into a polarization component aligned in a first polarization direction and a polarization component aligned in a second polarization direction perpendicular to the first polarization direction by means of the polarization separation element. Then, the polarization conversion element makes the polarization rotation element convert the polarization component aligned in the second polarization direction into a polarization component aligned in the first polarization direction, and thereby adjusts the polarization direction of the emitted light to coincide with the first polarization direction.
In such a polarization conversion element, as the polarization rotation element, organic material such as olefin or polycarbonate is sometimes used. However, when the organic material is used as the polarization rotation element, deterioration of the organic material and deterioration of an adhesive for bonding the polarization rotation element as a result of being illuminated with a light become a problem.
Therefore, for example, JP-A-2003-302523 discloses a technique using inorganic material such as quartz crystal as the polarization rotation element.
However, the polarization rotation element using the inorganic material is disadvantageous in that it is more expensive and has lower polarization conversion efficiency than the polarization rotation element using the organic material. Moreover, since the polarization rotation element using the inorganic material is also bonded by using an adhesive, it also suffers a reduction in reliability due to deterioration of the adhesive. In particular, a technique using a laser light source as a light source of the projector has been recently proposed, and deterioration of the polarization rotation element and the adhesive caused by a high-density light tends to become a problem.